Nonwoven fabrics



March 6, 1962 F. w. MANNING NONWOVEN FABRICS 2 Sheets-Sheet 1 Filed July5, 1957 INVENTOR.

March 6, 1962 F. w. MANNING NONWOVEN FABRICS 2 Sheets-Sheet 2 Filed July5, 1957 IN VEN TOR.

nited fitates 3,024,149 NUNWQVEN FABRIICS Fred W. Manning, PAH). Box125, Palo Alto, flalif. Filed July 5, 1957, Ser. No. 679,334 16 Claims.(Cl. llS6-28) My invention relates to nonwoven fabrics, particularly toreinforced nonwoven fabrics for use in surface and depth tyne magazinefabric filters for clarification purposes. This application is acontinuation-in-part of my copending application entitled FabricFilters, Serial No. 598.175, filed June 8, 1956, now abandoned.

By surface type I mean a fabric filter in which the first winding of abed of windings will retain all or most of the impurities of a fluidpassing therethrough, and from which bed fabric can be automaticallyremoved with sufficient frequency to maintain the flow rate constant.Depth type denotes a filter in which nearly the entire bed of manyfabric windings is used to remove the impurities, and the win-dings areautomatically advanced in a direction opposed to the flow of the fluidby adding fresh fabric to the fluid outlet surface of the bed andremoving contaminated fabric from the fluid inlet surface of the bedwith suflicient frequency to maintain clarity and flow rate constant.

The fabric may be made of any thickness but preferably is about .01 inchin depth, which will give about 100 windings to each inch depth offilter bed. The greater the effective depth of the filter bed, the moreporous is can be made and the greater will be the flow rate for anygiven clarity, and this flow rate can be further augmented by stretchingthe windings as they become clogged. Consequently, it was found that a3-inch depth of fi'ter bed of 300 windings in a counter-current type offabric filter will give from 3 to 10 times the filtering rate obtainedfrom other types of filters using one thickness of fabric forclarification purposes. For the above reasons, depth type countercurrentfabric filters are particularly suitable for the filtering of all kindsof aerosols.

Removal or renewal of filter bed windings during operation means thatthe fabric must have a reasonable amount of tensile strength.Accordingly, scrim or cheesecloth was used originally to reinforce andcarry a web of comparatively short fibres. But scrim is a woven fabricand was found to be altogether too expensive for windings that werediscarded after being extruded from a filter, and therefore it becameobvious that the much cheaper nonwoven webs of filaments would have tobe substituted.

In order that a web of fibres or other treating solids adsorb and retainthe maximum amount of impurities of a fluid passing therethrough, theweb first must be produced in like manner, i.e., by passage of a fibreconveying fluid through a foraminous, fibre-retaining wall to obtain theuniform distribution and penetration required for passage of thesecondary fluid from which impurities are to be removed. And to greatlyspeed up the said distribution, the fibres should be sifted firstthrough a primary foraminous wall while subject to agitation over thewall and movement of the conveying fluid passing through both walls.

But filaments of substantial length for reinforcing purposes cannot bepassed through the foramina of a primary sifting wall by agitation underpressure of a fluid passing through both walls, and therefore they mustbe deposited on the opposed side of the primary wall, and preferablyused as a secondary wall to retain the fibres sifted through the primarywall.

It is therefore an object of my invention to provide a method and meansfor depositing fabric making materials of treating solids andreinforcing filaments on opposed sides of a primary or siftingforaminous wall before passing one of the said materials through thewall to be united to the other of the said materials.

An additional object is to produce and deposit the said web of filamentson one side of a foraminous sifting wall immediately preceding, orsimultaneously with, the agitation of discrete fibres or other treatingsolids on the opposed side of the wall, and to utilize the said Web offilaments as a fibre retaining or secondary Wall when sifting the fibresthrough the primary Wall.

Another object is to provide an arrangement to utilize the entireperipheral area of a cylindrical wall for fibre deposition purposes andthereby greatly increase the formative speed of such laminated fabrics.

A further object is to provide a filter sheet of treating solidsreinforced by cold-drawable filaments that can be extended uniformlyduring use to increase its capacity for retaining or adsorbing solidimpurities.

A still further object is to cold-draw the bonding filaments a definiteamount in the manufacture of the fabric so that the finished fabric willnot only have strength but a predetermined extensibility.

An additional object is to produce an isotropic fibrebonded sheet, i.e.,a sheet having uniform strength in all directions of a two-dimensionalplane.

Another object is to attenuate fibre forming pellets into filaments bypropulsion of the pellets alone before their complete attenuation.

A further object is to produce discontinuous, reinforcing filaments ofmore uniform length, diameter, and strength than have been obtainable byprior methods.

And still another object is to provide a fabric of treating solids forbleaching, decolorizing, catalyzing, or other treatment of fluids sothat when the fabric is moved counter to the flow of the fluid through adepth filter the amount of such solids required is greatly diminished.

Other objects of my invention will become apparent from the followingdescription.

In accordance with certain aspects of my invention, fibres may be ofvegetable, animal, or mineral origin, and preferably are cellular ratherthan solid because of their greater adsorptive areas for the retentionof impurities. The fibrous material is conveyed in any suitable forminto an attrition mill or other fiberizing machine that will fluff orseparate one fibre from another, and when necessary shorten the fibres.

From the fiberizing machine an elastic fluid conveys the fibres onto adistributing and depositing foraminous wall. This may be an endless beltbut preferably is a rotating foraminous drum in which the fibres aredistributed over its inner surface and into its foramina by relativemovements of the drum and an agitator during pa sage through the drum ofthe said fluid.

A web of filaments is deposited by a propulsion stream directly on theouter or opposed surface of the wall, or in close proximity thereto andcarried onto the opposed surface. This web on removal from the wallretains the fibres deposited in its mesh and foramina of the wall, ortherebetween, and any fibre escape therethrough is carried by theconveying fluid back to the fiberizing machine and retained on and inthe said web by recirculation of the fluid through successive portionsof the web. When desirable, a cyclone or other separator may intervenebetween the fabric making machine and fiberizing machine and thecollected treating solids returned by blower to either the fiberizing orfabric making machine.

The filaments are preferably stretch-oriented before being deposited togive the web substantial strength. This can best be accomplished byattaching short fibers or other solids to one end of the filaments, orto filament-formingmaterial, and propelling such solids through aspinning or propulsion barrel. Sufficient stretch-orientation for manypurposes can also be obtained by the propulsion of Patented Mar. e,resa- 3 filament-forming pellets through a spinning barrel of sufficientheat and length to bring about the complete attenuation of the pelletsinto filaments.

Whatever the manner of stretch-orientation by propulsion of pellets orother solids, regular relative movements of the barrel and receivingwall will distribute and deposit the filaments so that they intersectand extend with substantial uniformity beyond, and in predominantalignment with,, one another, and if their depositing surface is movingwith sufficient speed in the same direction as the trailing filamentsthe latter can be made to intersect one another and still runsubstantially lengthwise of the fabric.

For most filtering purposes I have found that cotton linter dust on theorder of floor sweepings of less than V inch in length in mixture ofwith similar length asbestos fibres gave excellent results, providingthe amount of asbestos by weight was maintained between 25 and 33percent of the mixture. Of course, for many purposes it may be desirableto change this ratio or substitute other fibres and granular solids,such as glass, wood, sisal, rayon, shredded scrap leather, carbon,fullers earth, etc.; and the fibres may be of much greater length thanindicated above, especially when used for easily filtrable fluids.

The materials used for the production of filaments may be organic orinorganic, and thermoplastic or thermosetting, such as the usualplastics extruded or sprayed into filaments, films, and foils. Some ofthe most common of these are: polymeric amides, vinylidene chloride,polyethylene, polystyrene, glass, etc., spun from a molten state;cellulose-acetate, copolymers of vinyl-chlorideacetate resins, rubberhydrochloride, and other elastomers spun from solutions, etc.

Once a thermoplastic filament has become set, colddrawing will usuallybring such a filament to its initial point of elasticity, and from thereuntil its elastic limit has been reached it may be truly elastic.Therefore, extensible filament means a filament that can be extended; ina softened and adhesive condition, as by heat or solvent; in anonadhesive condition, as by cold-drawing; or by virtue of itselastomeric characteristics.

To give substantial strength and predetermined extensibility to anonwoven fabric, the filaments may be stretch-oriented a predeterminedamount during production; and heat, if used later for bonding purposes,should not reduce the temperature of the filaments to their softeningpoint and cause a loss of stretch-orientation. The extension of thefabric when in use may be due to softening under heat, additionalcold-drawing, elasticity of the filaments, or to any combination of suchfactors; but the amount of stretch-orientation during production mustnot be so great as to preclude its proper extension when in use.Furthermore, to give strength to the web, the filaments should havesubstantial length. This will usually range from 2 or 3 inches to manyfeet in length. The comparatively short length fibres bonded to or bythe filaments will usually vary from dust particles to those of one inchin length.

The bonding of short discrete fibres by extensible filaments in contacttherewith may be accomplished by: an adhesive spray; depositing thefilaments in an adhesive condition; depositing the filaments in acold-drawn condition and rendering them adhesive thereafter, asby aheated calender roll; incorporating in the treating solids, or thepropulsion stream for the filaments, a small percentage of potentiallyadhesive fibres or granular adhesive solids, preferably of lowersoftening temperature than the filaments, and rendering them adhesive bya heated calender roll at the said lower temperature; or by means of asuitable solvent, such as acetone, to bond cotton fibres to vinylfilaments. In the latter case, the bonding should be accomplished withina closed chamber in order to recover the solvent vapors.

Stretching of a fabric uniformly reinforced by extensible filaments byrenewal of filter bed windings after a certain amount of use, asdescribed in the above mentioned copending application, results in auniform increase in the spacing of the treating fibres or other solidsand their capacity for the retention of solid impurities.

The invention is exemplified in the following description, and preferredarrangements are illustrated by way of examples in the accompanyingdrawings, in which:

FIG. 1 is an elevational view, partly in section, of the complete fabricmaking equipment.

FIG. 2 is a vertical section of the fibre depositing apparatus taken online 22 of FIG. 1.

FIG. 3 is a vertical section of a modified form of the spinningarrangement shown in FIG. 1.

FIG. 4 is an elevational view, partly in section, of still another typeof spinning arrangement that may be used with the fibre depositing drum.

FIG. 5 is an elevational view of an eccentric arrangement used formoving the spinning barrel.

Referring to the drawings more specifically by reference characters:

As shown in FIGS. 1 and 2, fabric 1, to be made into short, discretefibers, is carried from roll 2 into a fiberizing machine 3, the rolls 4and variable speed transmission 5 regulating the feeding speed. Afterbeing shortened and separated the fibres are conveyed by air pressurefrom a blower 6 through pipe 7 into a depositing drum 8.

This drum is foraminous, having openings 9 therethrough, such as arefound in perforated plate, expanded lath, or heavy wire screen. It iscarried by left and right end plates 10 and 11, respectively, to whichare attached left and right sleeves 12 and 13, respectively, whichrotate in left and right journals 14 and 15, respectively, and thelatter are supported by left and right angle frames 16 and 17,respectively. Left and right flanges 18 and 19, respectively, arerigidly attached to the end plates and support a fibre agitator. Thisconsists of a rotating shaft 2!), brush bar 21, and brushes 22, the barbeing rigidly attached to the said shaft by angle irons 23 and 24. Theright hand sleeve is closed by a bearing plate 25 which also supportsthe agitator shaft, the latter being driven through a sprocket wheel 26and chain 27 from a source of power not shown. In somewhat similarmanner, the left hand end sleeve is equipped with a sprocket wheel 28which is driven by chain 29 from a source of power not shown.

The depositing drum is enclosed by a casing 30, the upper end portionsof which support left, center, and right calender rolls 31, 32, 33,respectively. An endless foraminous belt 34 is carried over rolls 35 andthe latter are supported by brackets 36 attached to the drum casing. Aweb 37 of reinforcing filaments 38 formed on the belt is carried by thelatter into the casing between the center and right calender rolls, andafter being carried around the drum and coated by short fibres or othersolids 39 leaves the casing between the left and center calender rolls,as fabric 40. The fibre conveying fluid is propelled by force of blowerpressure from the casing through outlet 41 into a pipe 42, both of whichrun lengthwise of the casing under the belt, and is returned to thefiberizing machine through pipe 43 connected to the end of tube 42. Anadhesive spray is shown at 44 whose length is the width of thefilamentary web.

The filament forming apparatus shown in FIG. 1 consists of a lower rotoror foraminous drum 50 which rotates about the stationary arms 51, 52,53, and 54, the drum and arms thereby forming: three suction chambers55, 56, and 57, the first and last being connected through openings 58in arms 52 and S3 with the center chamber 56 and its source of suction59; and a blowing chamber 60 having an opening 61 to a source of fluidpressure. The drum rotates upon rolls 62, one or both of which aredriven from a source of power not shown, and the rolls with casing 63form a depositing chamber for fibers or other solids, which may bebypassed from the attrition mill 3.

The top rotor 64 rotates in contact with the lower rotor and upon afixed hollow shaft 65 having an inlet 66 for heating fluid, and isequipped on its peripheral surface with pockets or reservoirs 67 for thematerial fed therein from a feeding cylinder 68. This cylinder enclosestwo feeding pistons 69 and 70 through which a filament forming rod 711is moved forward and brought to filament forming fluidity by a heatingfluid, such as steam, in the annular chamber 72. This feedingarrangement is described in my US. Patent No. 2,437,263, issued on March9, 1948.

As the rotors move through divergent paths short discontinuous filaments73 are formed which are attenuated into long discontinuous filaments 7by the propulsion of discrete solids 75' from the lower rotor. A casing'76 is used to enclose both rotors and is extended on one side to form abarrel 77. A flame from a jet 78 may be used to cut any trailingfilaments from nonexhausted pockets. The barrel leads into an ejector'79 having an inlet 34? and an outlet $1 which is connected by aflexible connection 82 to a distributing pipe 83. This pipe is movedback and forth over the depositing belt by means of (see PEG. strap 84,connecting rod 85, eccentric strap 86, and eccentric 87, the latterbeing driven from a source of power not shown. A suction box 825 ispositioned under that portion of the depositing belt moving across theoutlet of the distributor pipe, and has a connection 89 to a source ofsuction.

In FIG. 3 the rotors are the same as in FIG. 1 but in reverse position,there is no opening in arm 53, and chamber 57 is not subject to suction.Discrete solids are deposited on the suction roll by belt 9% passingover the roll 91, and filament forming material 92 is introduced into ahopper 93 in discrete and finely divided portions, as from St to 20%mesh. The rate of feed of this material is regulaed by rotary valve 94at the entrance to the feed pipe 95, and the material is delivered infibre-forming fluidity against the periphery of the rotor by a blastfrom the burner 96, which is supplied by fuel and air under pressurethrough pipe 97 from a source of supply not shown. A scraper 98,pressured by a spring 99, removes excess from the surface of the rotorand the drip escapes through a drain ltltl in the refractory wall 101and steel casing Hi2.

FIG. 4 shows an arrangement in which the filaments are distributed onthe belt directly from a feeding arrangement, similar to 68 shown inFIG. 1 and described in the above mentioned patent, except that anejector 103 with a fluid blast inlet TM is used to disrupt thefibreforming fluid material into filaments and force them through adistributing pipe lltlS without the aid of pulling solids. Straps 84connected to the eccentrics, shown in FIG. 5, give the spinning gun alateral movement across the top of the belt.

The operation of the apparatus described above has been indicated, inpart, in connection with the foregoing description. The followingexamples will more completely illustrate the methods that can be used inthe practice of my invention.

Example I Filter fabrics comprising a mixture of cotton and asbestosfibres and bonded by polyarnide filaments can be manufactured by thearrangement shown in FIG. 1.

Short asbestos fibres of less than inch in length are carried by an aircurrent from a blower not shown into the casing 63, and deposited onthat portion of an 18-inch diameter foraminou drum 58 passing throughthe orbit of the casing. This is accomplished under a differentialpressure produced by the blower and/ or suction from the chamber 55,having open connections described above to suction outlet 59. As thedrum rotates fresh fibres are deposited in the same way on successiveportions of the drum and are held in position by the said differentialpressure as the drum rotates about interconnected suction chambers 55,56, and 57.

A polyamide rod inch in diameter is propelled through the heating zoneof the cylinder 68 by the feeding pistons 69 and 70, described in theabove-mentioned patent, where it is brought to filament-forming fluidityat a temperature of about 290 F. The fluid polyamide is then forced intopockets 67 of about A; inch in diameter on the peripheral surface of asecondary 18-inch diameter rotor 64, heated to a similar temperature bysteam in the axial shaft 65.

Contact between the pocket charges and the fibres held by suction on theadjacent rotor with the rotors moving through diverging arcuate paths ata speed of 60 r.p.m. cold-draws the fluid charges of the pockets intofilaments '73 of from 15 to 18 inches in length. Propulsion of thefibres adherent to one end of the filaments, as the drum moves over thepressure chamber 60, greatly increases the attenuation of the filaments,particularly if the blast occurs slightly in advance of exhaustion ofthe pockets, or shearing of the filaments by jet flames 78.

This propulsion means is a blast of elastic fluid below the softeningpoint of the filaments, 275 F. in the present example, such as air ornitrogen at room temperature, saturated steam, etc., and is ofsufficient force to give the fibres a theoretical initial velocity of20,000 feet per minute, and increase the attenuation of the filaments bycold-drawing them to within a predetermined percent of the initial pointof their elasticity. The extent of colddrawing of the filaments 73 tofilaments 74 can be regulated by temperature, the size of the pocketcharges, force of the blast, and the time elapse between blast andseparation of the filaments from the upper rotor. The potentialcold-drawable stretch of the filamentary web should be at least 10percent for later extension in sixfoot diameter depth filters, and up to25 percent for later extension in laboratory size depth filters.However, sometimes it may be found desirable to cold-draw the filamentsto their initial point of elasticity and depend altogether on theirelastic stretch for extension when in use.

Under pull of fibres adherently connected to one end of the filaments,the latter will move endwise through the propulsion chamber and aredeposited in an integral web 37 on the foraminous belt 34 as the lattertravels over suction box 88. The belt with enclosed drum preferablytravel at a speed at least equal to that of the filaments in thedistributing pipe 83 at the time of their deposition; and lateralmovements of the pipe actuated by eccentric 87 through straps 36, 85,and 84, will result in the belt being coated uniformly. In such a case,the filaments will be found to extend beyond one another fairlyuniformly in a succession of overlaps, and to run predominantly inalignment with one another and substantially lengthwise of the belt, asshown by the filaments 38 from which the fibre coating 39 has beenremoved in FIG. 2.

A sheet of cotton linter dust, in which is incorporated 5 percent byweight of short length polyethylene fibres, is fed from roll 2 into anattrition mill or other fiberizing machine 3 where the fibres areseparated one from another. They are then carried by an air current fromthe blower 6 through pipe '7 into the foraminous drum 8 of about 6 feetin diameter and rotating clockwise between 5 and 10 rpm.

The blower pressure, aided by suction from pipe connection 43 androtation of the brush shaft, preferably in a direction opposed to thedrum movement, results in the fibres filling the openings or foramina ofthe drum and being retained in and by the mesh of the filamentary web 37described above which encircles the drum and with the aid of the beltbacking holds the deposited fibres against the blower air currentpassing through web and belt. As the openingsin the drum are flared out-7 wardly and the fibre filling are tied in with the fibres held in themesh of the filamentary web, the fillings readily leave with the web asit separates from the drum by movement between calender rolls 31 and 32.

Calender rolls 31 and 32 are steam heated internally sutficiently tobring the fabric as it passes therebetween to a temperature of 230 F.The heat and pressure of the rolls result in the foramina fillings beingsmoothed out and consolidated and the small percentage of polyethylenefibres becoming activated and adhesive, and bonding the linter dust tothe polyamide reinforcing web without softening and loss ofstretch-orientation to the polyamide filaments. Obviously, a granularthermoplastic can be substituted for the polyethylene fibres andintroduced into the linter dust and activated in the same way.

However, it is usually desirable that there should be as little bondingas possible of fibres or other treating solids in filter fabrics forsuch bonding always reduces the adsorptive areas of the fabric.Therefore, better results can be obtained usually by depositing thereinforcing filaments as a very open mesh web and in a suflicientlytacky condition to bond the filaments together and to the sifted fibres.In this tacky condition results from the high temperature of thespinning operation, curing can be effected at the time the Web is passedbetween the water cooled calender rolls 31 and 32. If the filaments aredeposited on the belt in a nonadhesive condition and made suflicientlyadhesive for the said bonding purposes by a liquid epoxy or other resinspray from nozzle 44, the curing can be effected either at roomtemperature, or by rolls 31 and 32 heated to a temperature just belowthe softening point of the filaments.

Or for purposes where maximum strength of reinforcing web is notrequired, the temperature of the calender rolls 31 and 32 can be carriedsufliciently high, 290 F. in the present example, to make the filamentstacky, but with loss of stretch-orientation. In any event, the bondingfor filter fabrics preferably is at the fluid outlet surface of thefabric, and the curing accomplished by heated rolls 31 and 32 for athermosetting adhesive resin, or chilled rolls 31 and 32 for athermoplastic resin.

The total amount of asbestos used to aid in the attenuation of filamentforming material and introduced with the linter dust should be between25 and 33 percent of the total weight of the finished fabric forordinary filtration purposes. Because of the thinness of the fabric, themethod of introduction of the asbestos fibres will not greatly affectits filtering characteristics as long as it is uniformly distributed.However, to speed up the manufacture of fabric, as much as possible ofthe asbestos fibres should be incorporated with the linter dust by wayof fiberizing machine 3.

Obviously, bleaching, decolorizing, and other treating solids, such asfullers earth, bone char, etc., with or without a mixture of fibres, canbe sifted and deposited through the foraminous drum 8, and bonded by afilamentary web as described above for fibres alone. When such solidsare used in windings that move counter to the flow of fluid passingtherethrough, the amount will be greatly diminished and often can be cutin half.

Example 11 Leather replacement compositions for handbags, brief cases,luggage, etc., can be made from shredded waste leather reinforced by athermoplastic material, such as polyamide filaments, in much the sameway as indicated by the above example.

Waste leather is fed into the attrition mill 3 where it is shredded tofibres of any suitable length, as for instance to /2 inch, and thenconveyer into the foraminous drum 8, in mixture with an elastomericbinder, such as polyethylene fibres. Since the fibres are much longerthan in Example I, the openings in the drum preferably may be slotsmilled of suitable length and width and outwardly flared for easy exitof the fibres under agitation and air pressure. A coiled wire drum withcoils spaced inch apart and spot-welded together every two inches willalso be found suitable for such a purpose.

If reinforcing filaments of only moderate strength are required, thespinning gun shown in FIG. 4 and described in my US. Patent No.2,437,263 can be used. A polyamide rod 71 is propelled by pistons 69 and70 through cylinder 68 in which it is brought to filamentformingfluidity at a temperature of about 290 F. and is then subjected to ablast of saturated steam from ejector 103 which produces filaments ofvarious lengths in a tacky condition for their bonding into an integralweb under pressure and curing of the calender rolls 32 and 33. Theserolls may be coated with polytetrafluoroethylene to prevent sticking ofthe filaments. The shredded fibres are bonded together and to the saidintegral web by the polyethylene fibres under pressure and heat of 230F. from the calender rolls 31 and 32. Obviously this temperature issufficient to aid the above curing of polyamide filaments.

With this type of spinning gun, the filaments cannot be deposited inalignment with one another but the lateral movements of the propulsionbarrel through pull on eccentric straps 84, with the forward movement ofthe belt 34, will result in the filaments overlapping, intersecting, andextending beyond one another with substantial uniformity.

Example III In the manufacture of chairs, soft facings of leather,cotton, rayon, etc., for comfort can be produced, as indicated inExample II; and these facings may be laminated for strength to glassbackings which can be produced by the apparatus of FIG. 3.

In FIG. 3 a suflficient amount of asbestos fibres for propulsionpurposes is conveyed on the belt and uniformly distributed over suctionareas of a rotor 50, described above. Small discrete particles offibre-forming glass 92, such as from 100 to 200 mesh, are charged intothe hopper 93 and fed as required by rotary valve 94 through pipe 95 tothe burner 96, which is supplied by fuel under pressure by pipe 97 froma source of supply not shown. The blast of burning fuel reduces thediscrete particles of glass to a fibre-forming fluidity at a temperatureof about 1900 F., and in that condition they are deposited on theperipheral surface and in the pockets of a bottom rotor 64; or theparticles, if deposited in a solid condition, will adhere to and bereduced to fibre-forming fluidity by the rotor heated to about 2100 F.from a series of jet flames 78 or other suitable means. The molten glassin either case is scraped by a spring pressured blade 98 into thepockets 67, and the excess is removed entirely from the rotor anddrained through outlet 100.

Converging paths of the two rotors bring the discrete asbestos fibresand the pockets filled with filament-forming glass into adhesivecontact, and their diverging paths cause the glass in their respectivereservoirs to neck down into positively stretched filaments 73 untilfinally the fibres are cut off from their suction contact with theperipheral surface of the top rotor and blasted therefrom by heated airor steam pressure within the pressure chamber 60. The blast gives thefibres a theoretical initial velocity of at least 20,000 feet perminute, and the force exerted on the fibres, to which the filaments areadhesively connected, produces filaments 74. Both are deposited at atemperature of about 230 F. and bonded to a sifted leather web,described in Example II, by an epoxy resin in granular form introducedby ejector 79 and brought to an adhesive temperature at the saiddeposition temperature for the glass filaments; and the resin is curedat room temperature. When desirable, short chopped glass fibres,perlite, metal flakes, micaceous materials, etc., of higher softeningtempera- 9 ture than the filament-forming glass, can be substituted forasbestos.

Obviously, a solid rotor similar to 64 but without pockets can besubstituted for the foraminous rotor 50, and the charges 67 given apositive attenuation by contact with the substituted rotor. In such acase, jet flames 78 are used to Shear the filaments 73 from the rotors,and the propulsion blast can be introduced at any convenient locationbetween the shearing points.

It will also be obvious that a filamentary web may be deposited directlyon the foraminous drum 8, providing a suction chamber, such as 56, isincorporated within the drum; but in such a case, the movement of theagitator brush would be restricted and it would have to oscillate backand forth without moving through an endless circuit.

The above examples are descriptive of various ways in which thepropulsion of adherent solids can be used to attenuate filament-formingmaterial into filaments, stretch-orient the filaments, and propel thestretchoriented filaments endwise through a propulsion tube to aid intheir deposition in intersecting relation and predominantly in alignmentwith one another.

However, it is obvious that filament-forming material in pellet form,without the aid of pulling solids, can also be attenuated into filamentsand the filaments stretchoriented and propelled endwise through thepropulsion barrel, providing attenuation is completed just prior todeposition, and the filaments will be deposited in intersecting relationand predominantly in alignment with one another.

To produce such filaments only the lower rotor, shown in FIG. 1, isrequired, the pellets being brought into contact with the suction areasof the drums periphery in any suitable manner, as by blower conveyancethrough casing 63. The pellets in nonadherent condition are propelledfrom the rotor with sufiicient force to carry them through the ejector,at which point they are subjected to a more forcible blast ofsuperheated steam at suflicient temperature to reduce them to a fluiditythat will produce trailing filaments during flight through a propulsionbarrel of substantial length. This temperature for the polyamidefilaments of Example III will be somewhere between 400 F. and 500 F. fora -foot length propulsion barrel, the entire surface of which may begiven a coating of polytetrafluoroethylene to prevent sticking theretoof the filaments, and of course the greater propulsion force willcentralize the flow of the filaments.

Or the pellets may be deposited in the pockets or dis tributed on theperiphery of the one rotor 64 with only a surface portion of the pelletssufliciently tacky to adhere to the rotor, and the rotor speeded up to3,000 rpm. or more to throw off the pellets by centrifugal force. Thepull of the pellets will produce stretchoriented, pellet-entrainedfilaments, and the heat and blast from the ejector will increase thelength of the filaments as the pellets are attenuated into filaments. Ofcourse, the pellets may be deposited on the rotor 64- infilament-forming fluidity and then thrown off by centrifugal force, butthe filaments will not have the length or stretch-orientation possessedby 'solid, surface-adherent pellets thrown off, as described.

Obviously, one of the main fabrics of my invention consists of a web ofuniformly distributed fibres positioned at random to make the fabricuniformly fluidpenetrable, and bonded to stretch-oriented, intersectingfilaments predominantly in alignment with, and extending beyond, oneanother in a succession of overlaps. Such fabrics may have substantiallyuniform strength in all directions of a two-dimensional plane, and, ifso, would be considered isotropic in that plane.

It will be understood throughout the specifications and appended claimsthat: short fibres mean fibres that are short in length in comparison tothe reinforcing filaments that give strength and bonding to the saidfibres;'

and random fibres means fibres whose axes exist in all three dimensionalplanes. Short nonbinder fibres will usually be less than of an inch inlength, the binder fibres somewhat longer, and neither, as a rule, willexceed one inch in length. The reinforcing filaments will vary fordifferent purposes between several inches and many feet in length. TheWord contiguous means in actual contact.

I claim as my invention:

1. In a method of making a nonwoven fabric from different types ofdiscontinuous fibres, the steps comprising: continuously moving aforaminous wall through an endless path; depositing discontinuousprimary and secondary fibres on opposed surfaces of the said wall duringthe said movement, the primary fibres intersecting one another atrandom, and the secondary fibres successively intersecting andoverlapping one another with sufficient uniformity in a two-dimensionalplane to form a foraminous web of substantial strength; moving the saidweb in contiguous relation with one side of the said wall, andsimultaneously agitating the primary fibres on a side of the wallopposed to the said one side while conveying the fibres in measuredamounts into the foramina of both wall and Web by force of a fluidstream passing through the wall and Web; and consolidating and bondingthe primary fibres with substantial uniformity about the said web ofsecondary fibres whereby the primary fibres are reinforced by thesecondary fibres to form the said fabric.

2. The method of claim 1 in which one of the said types of fibrescontains potentially adhesive solids, and including the step ofactivating the said potentially adhesive solids to accomplish the saidbonding.

3. The method of claim 1 in which the said primary fibres are a mixtureof binder and nonbinder fibres, the binder fibres being potentiallyadhesive, and including the step of activating the said binder fibres toaccomplish the said bonding.

4. The method of claim 1 including the step of removing the said primaryfibres from out of the said foramina of the wall, subsequent to theirbonding to the said web, by movement of the said web away from the wall.

5. The method of claim 1 in which the said primary fibres are natural,and the said secondary fibres are thermoplastic and selected from thegroup consisting of polymeric amides, vinylidene chloride, polyethylene,polystyrene and glass.

6. The method of claim 1 in which the said primary fibres are by weight67 to 75 percent cotton in mixture with 33 to 25 percent asbestosfibres, and the said secondary fibres are polyamide fibres.

7. The method of claim 1 in which inorganic solids selected from thegroup consisting of glass, asbestos, perlite, micaceous and metallicmaterials are bonded in the said fabric by at least one of the saidtypes of fibres.

8. The method of claim 1 in which the said secondary fibres arestretch-oriented and of predetermined softening point, and at least aportion of the said primary fibres are potentially adhesive and arebinder fibres of lower adhesive temperature than the said softeningpoint, and including the step of activating the said binder fibres atthe said lower temperature Without loss of the said stretch-orientation.

9. In a method of making an extensible nonwoven fabric, the steps ofclaim 1, and including the step of attenuating fibre-forming materialinto the said secondary fibres, the fibres being cold-drawable andhaving predetermined potential stretch.

10. The method of claim 9 including the steps of: adherently contactingdiscrete solids to finely divided portions of the said material; andpropelling the said solids to accomplish the said attenuating.

11. The method of claim 9 in which the said material is in the form ofpellets, and the said attenuating is accomplished by propelling thepellets through an atmos phere heated sufficiently to reduce the pelletsto fibreforming fluidity.

12. The method of claim 9 in which the said attenuating is accomplishedby centrifugal force supplemented by force of an elastic fluid stream.

13. In an apparatus for making a nonwoven fabric from different types ofdiscontinuous fibres, the combination of: a foraminous Wall movingthrough an endless circuit through which wall primary discontinuousfibres may be conveyed; means for depositing a foraminous web ofreinforcing secondary discontinuous fibres on one side of the said wall;means for conveying the said web contiguously with the said one side ofthe wall through a portion of the said circuit; means for agitating theprimary fibres on a side of the wall opposed to the said one side whilethe fibres are subject to the force of a fluid stream to convey thefibres in uniform amounts into the foramina of the wall and web duringthe said contiguous conveyance of the web; and means for consolidatingand bonding the said amounts of primary fibres about the said web ofreinforcing fibres.

14. The combination of claim 13 for making the said nonwoven fabric, inwhich the said wall is a primary wall, and including: a secondaryforaminous wall, adjacent to the said primary wall, moving through anendless circuit, and on which wall the said web is formed; and means fortransferring the said Web from conveyance on the secondary wall to thesaid contiguous conveyance on the primary wall during the said movementsof both walls.

15. The combination of claim 13 for making the said nonwoven fabric inwhich at least a portion of the said primary fibres are potentiallyadhesive, and including means for activating the said potentiallyadhesive primary fibres to accomplish the said bonding.

16. The combination of claim 13 for making the said nonwoven fabric inwhich at least a portion of the reinforcing secondary fibres arepotentially adhesive, and including means for activating the saidpotentially adhesive secondary fibres and maintaining them in anadhesive condition during the formation of the said web on the secondarywall to cause the said reinforcing fibres to be bonded one to another inan integral web.

References Cited in the file of this patent UNITED STATES PATENTS1,448,203 Curnfer et a1 Mar. 13, 1923 2,055,410 Hurst et al. Sept. 22,1936 2,056,275 Holdsworth Oct. 6, 1936 2,336,743 Manning Dec. 14, 19432,489,079 Clark et a1. Nov. 22, 1949 2,543,101 Francis Feb. 25, 19512,687,363 Manning Aug. 24, 1954 2,750,317 Manning June 12, 19562,765,247 Graham Oct. 2, 1956

13. IN AN APPARATUS FOR MAKING A NONWOVEN FABRIC FROM DIFFERENT TYPES OFDISCONTINUOUS FIBERS, THE COMBINATION OF: A FORAMINOUS WALL MOVINGTHROUGH AN ENDLESS CIRCUIT THROUGH WHICH WALL PRIMARY DISCONTINUOUSFIBRES